Vapor electric device and method of operation



April 18, 1944. R N ET AL 2,347,048

VAPOR ELECTRIC DEVICE AND METHOD OF OPERATION Original Filed March 28,1941 Inventors: i Newell T. Gordon,

32 Willis Rwhibneg,

Th eir- Attorney.

Patented Apr. 18, 1944 VAPOR ELECTRIC DEVICE .AND 'METHOD OF OPERATIONNewell T. Gordon and Willis R. Whitney, Schenectady, N. .Y.,assignorsr-to General Electric Company, a corporation .of New -York 1Original application March 28,1941, Serial No.

385,642. Divided and this application November '10, 1942, Serial No.465,114

9 Claims. (01. jive-#122) The present application is a division of ourprior application Serial No. 385,642, now Patent No. 2,307,502, andrelates to vapor electric devices, such as mercury lamps, and inparticular to devices of this type which are operated at relatively highvapor pressures. our invention is applicable with especial benefit tohigh pressure vapor lamps which are provided with an envelope ofsubstantially capillary dimensions in which under operating conditionsthere is a pressure of at least several atmospheres. High pressure lampsare described in B01, Elenbaas and Lemmens United States Patent No.2,094,694, issued October 5, 1937, and in Germer United States PatentNo. 2,202,199, issued May 28, 1940.

It is the object of our invention to provide an improved apparatus and amethod whereby vapor devices may be maintained at a desired operatingtemperature. In the operation of vapor electric devices of high wattageconsumption, it is necessary to carry heat away more rapidly than thenatural rate of heat dissipation. The progressive increase of vaporpressure otherwise would result in correspondingly increasing thevoltage necessary to operate the lamp. Assuming a superatmosphericpressure lamp to be operated from a supply circuit of high reactance, iteventually would be extinguished. In that event the device would notrestart until it had cooled and the vapor pressure had, fallenconsiderably lower than the pressure at which it ceased to operate. Thiswould result in unsatisfactory intermittent operation.

Another source of diiliculty encountered in the operation of highpressure lamps is the devitrification of such-parts of the envelope asare in contact with the discharge, the devitrification being especiallymarked in the neighborhood of, the electrodes. In the forms of highpressure lamps shown in the above-mentioned B01 et al. patent in whichthe pressure of mercury vapor reaches many atmospheres during normaloperation, the heat dissipation requirements are especially exacting.

High pressure lamps may be cooled by the circulation of water over theirsurfaces, such arrangement being described in B01 and Lemmens UnitedStates Patent No; 2,094,695, patented October 5, 1937. Ordinarily, highpressure mercury lamps constructed to operate with a loading of morethan 200 watts per centimeter of discharge column have beenwater-cooled. Itisinconvenient and in some cases it is inefiicienttowater-cool vapor electric devices. ,Water, although an efiicient coolingmedium, is subject to freezing. Also, water and other cooling fluids aresubject to fo'uling, especially when recirculated in a closed'system.Furthermore, liquid cooling is apt to be too energetic at the regionwhere unva poriaed material, such as mercury, is present. Ordinary aircooling, that is, cooling by air circulation, such as may be produced bya fan, 'is not sufficiently effective, particularly in lamps in whichthe discharge tube is of small bore as indicated in Fig. l and pressuresof mercury vapor of at least several atmospheres are normally presentduring operation.

As aconsequence of our invention, we have providedimproved gas-coolingmeans, conveniently using air as the cooling medium, by the use of whichvapor electric'devi'ces may be operated at high pressures withmaterially higher wattage inputs than heretofore possible. Anotheradvantageous result of our'inve'ntion is a reduction of devitrificationof the lamp envelope which, as stated in the above-mentioned Patent2,094,694, may consist of vitreous silica or heatresisting glass.

. As will be pointed out in greater particularity inthe appended claims,the main novel feature of our invention comprises a method of andapparatus for applying to a vapor electric device high velocity jets ofcooling fluid, preferably air, the cooling jet having a dimension whichis materially smaller than the surface which is being cooled. The claimsin the present application are directed particularly to a modificationof our invention whereby a high velocity jet of cooling air is directedagainst the envelopeintermediate' said electrodes. The nozzle orifice ispositioned so closely adjacent the surface to be cooled that the area ofimpingement of the jet is substantially the same or-but little greaterthan the diameter of the jet.

Several embodiments of our invention are shown in the accompanyingdrawing in which Fig. 1 shows a vapor lamp and jet cooling means in sideelevation; Fig. 2 shows such combination mounted in a light projector;Fig. 3 is a partly sectionalized side view on an enlarged scale of amodification in which part of a tubular lamp is coated withalight-"reflecting layer; Fig. 4 is a cross section on lines 4"'-4 ofthe modification of Fig.- 3; and Figs. 5 and 6 are perspective views of,nozzles for furnishing cooling jets.

The lamp shown in Figs. 1, 2 and 3 comprises a tubular envelope. 2provided at opposite ends respectively with electrodes 3, 4 which mayconsist of tungsten. The envelope 2' ordinarily consists -01 vitreous orfused quartz, although heat-reof mercury is adjusted during themanufacture of the lamp. The electrodes 3, 4 project about onemillimeter beyond the mercury surface. The

envelope also contains a charge of starting gas,-

such for example as argon or neon, at a pressure of about 50 millimetersof mercury. The lamp is supported by electrically conductive supportsl3, M, on the ends of which it is held by spring clips l5, 15. Operatingcurrent is supplied by the conductors ll, l8 connected to the contactter-' minals I9, 20. The supports l3, l4 aremounted on an insulatingbasell. Such a device may be operated at a pressure exceeding 40atmospheres and up to 200 atmospheres and higher.

Unless the envelope of such a device is energetically cooled, it willcontinue to rise in temperature upon being put into operation, thevoltagerequired to operate the device. rising at the same time. Thisrise in vapor pressure would result in extinguishing the discharge aftera short period of operation, or, if sufiicient voltage should be.available, excessive rise of internal pressure would cause the envelope-to.burst.

Effective cooling and continuous operation may be obtained by directingsharply localized jets of compressed air, or other suitablecooling'fluid, against the envelope'ofsuch device as shown in thedrawing. These jets'of air, delivered by the nozzles 22, 23 and suppliedby a pipe 24, should be directed substantially perpendiculanto the axisof the envelope. Although nozzlessuch as shown in Fig. 1 are ordinarilypreferred, .the jets may be modified in some cases asshownat 22 and 23',Fig. 6. Satisfactory jetcooling has been afiorded by maintainedpressuresof to.40 pounds. The jets of air may havea diameter of about].50 to 80mils. Preferably the centers of therespective jets of air are locatedopposite'the ends of the respective electrodes. When theends ofthenozzles are lengthened to form slits, as shownin Fig. 6, a modifyingeffect can be exerted upon the. vapor' pressure and electrical parentlya layer of warmed air, which tends to normally adhere to the surface tobe cooled, must be effectively and rapidly eroded away. The jets ofpressure air have an effective bufiing action which we have found to beabsent in the usual forms of air circulation. Surprisingly, such 10-calized jets adequately cool the envelope portion between theregions onwhich the jets impinge.

As shown in Fig. 2, the described lamp and the jet-cooling adjuncts maybe mounted in a light projector having a housing26 provided with theusual reflector (not shown) and mounted on the supports21, 28.

The lamp shown in Fig. 1 can be operated with a lighting efficiency of86 lumens per watt of consumed electric energy and with brillianciesover 50,000 candles per square centimeter. Because of this highbrightness, it is well adapted for use in searchlights.

In our application Serial No. 385,642, filed March 28, 1941, claimshavebeen made on the embodiment of our invention which is shown inFig. 1. In this species of device compressed cooling air is jettedagainst the envelope at regions adjacent said electrodes. In the presentapplication, we are directing claims to a modified embodiment in whichthe cooling air is jetted upon the region of the envelope in which thedischarge occurs, that is, the region of the envelope whichisintermediate the electrodes.

The lamp shown in Figs. 3 and 4 is in most respects similar to the lampshown in Figs. 1 and .2, but differs therefrom in two main aspects.

First, the envelope 2 is provided over approximately half of itscircumferential surface with a coating 39 of light-reflecting material,such as platinum or gold, which extends longitudinally over thedischarge space between the electrodes. Second, the jets of coolingfluid delivered by two nozzles 3|, 32 extend linearly substantially overthe entire discharge distance between the electrodes. The cooling jetsof air or other suitable fluid preferably are delivered tangentially asshown in Fig. 4. As appears in the drawing, the jetted cooling air isdistributed substantially symmetrically with respect to the midlength ofthe envelope so that corresponding points toward the. opposite endsreceive substantially equal cooling.

In Fig. 5 is shown in perspective the nozzle 3| with its slit-shapedopening, 34 carried by the supply tube 35. When employing a slit-shapednozzle the width of the slit should be materially less than the diameterof device to be cooled. In the particular case illustrated, its width isabout one-fifth the diameter of the lamp,

In both modifications of our invention the portion of the envelope ofquartz, or other refractory material, extending between the electrodesis cooled either locally or throughout its length by the impingement ofone or more high velocity jets which, however, exert but little coolingeffect on the masses of mercury or whatever vaporizable material may beemployed in the device.

- What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A method of operating a high pressure electric discharge devicecomprising a tubular heatresistant vitreous envelope containingelectrodes adjacent its ends, and also containing starting gas andmercury, which method consists in operating the device with an energyinput sufficient to maintaina discharge-constricting superatmosphericpressure of mercury therein, whereby devitrification of the envelope isentailed, jetting compressed cooling air externally against saidenvelope intermediate said electrodes with a conby the energy inputaforesaid.

2. A method of operating a high pressure electric discharge devicecomprising atubular heatresistant vitreous envelope containingelectrodes adjacent its ends, and also containing starting gas andmercury, which method consists in operating the device with an energyinput sufficiently high to maintain a discharge-constrictingsuperatmospheric pressure of mercury therein, and to produce substantialdevitrification of the envelope, jetting compressed cooling airexternally against said envelope intermediate said electrodes with aconstricted air stream width, transversely of the envelope,substantially less than the envelope width presented to the impingingair, distributing the cooling air substantially symmetrically lengthwiseof the envelope with respect to its mid-length, and maintaining thevelocity of air jet delivery sufilciently high to substantially reduceenvelope temperature and devitrification while allowingdischarge-constricting internal pressure to be maintained by the energyinput aforesaid.

3. A method of operating an electric discharge device comprising atubular vitreous envelope containing electrodes adjacent the endsthereof and also containing starting gas and mercury, which methodconsists in operating said device with an energy input sufliciently highto cause said envelope to be heated to a temperature at whichvolatilized mercury therein will have a pressure of at lea-st severalatmospheres, projecting a stream of compressed cooling air externallyand transversely against the portion of said envelope which isintermediate said electrodes, the width of said stream beingsubstantially less than the envelope diameter, and maintaining thepressure of such cooling air at about to 40 pounds, thereby avoiding thedevitrification of such envelope While maintaining a predetermined highoperating pressure therein.

4. A high pressure vapor electric discharge device comprising a tubularheat-resistant vitreous envelope containing electrodes adjacent itsends, and also starting gas and mercury for providingdischarge-constricting superatmospheric pressure in the envelope duringnormal operation, in combination with nozzle means for jettingcompressed cooling air externally against said envelope intermediatesaid electrodes with a constricted air stream Width, transversely of theenvelope, substantially less than the envelope width presented to theimpinging air, whereby envelope temperature and devitrification aresubstantially reduced while maintenance of dis-charge-constrictinginternal pressure is allowed.

5. The invention as set forth in the next preceding claim furthercharacterized in that the distance of the nozzle means from the envelopeis so short that the Width of air jet impingement on the envelope issubstantially the air jet width.

6. A high pressure vapor electric discharge device comprising a tubularvitreous envelope containing electrodes adjacent its ends and alsostarting gas and mercury for providing superatmospheric pressure in theenvelope during normal operation, said envelope having a coating oflightreflecting material covering approximately half the circumferentialsurface thereof and extending longitudinally over the discharge space insaid envelope, and means for projecting a fiat jet of compressed coolingair externally against said envelope intermediate said electrodes, saidjet having a width transversely of said envelope less than the envelopediameter, whereby envelope temperature is reduced without preventing thedevelopment of desired normal high pressure.

'7. A vapor electric device comprising an elongated tubular envelope,electrodes therein positioned near the ends thereof, a current-carryingmedium therein including mercury, and means :for supplying air underpressure to cool said envelope at a region between said electrodes, saidmeans including one or more nozzles for delivering constricted air jets,each nozzle having a slitshaped opening the transverse dimension ofwhich is less than the diameter of said envelope, the distance betweensaid opening and the envelope being so short that the width of air jetimpingement is substantially the air jet Width.

8. An electric discharge device comprising a tubular vitreous silicaenvelope, electrodes having stems sealed into opposite ends of saidenvelope, argon gas and mercury in said envelope, said device beingconstructed and proportioned to operate normally at superatmosphericpressure, and nozzle means constructed to project a jet of cool ingfluid or linear extension externally against said envelope, thetransverse dimension of said jet being less than the diameter of saidenvelope, said nozzle means being so positioned closely adjacent saidenvelope as to deliver cooling fluid tangentially with respect to saidenvelope.

9. A high pressure vapor electric discharge device comprising a tubular,heat-resistant, vitreous envelope containing electrodes adjacent itsends, and also starting gas and mercury for providingdischarge-constricting superatmospheric pressure in the envelope duringnormal operation, in com bination with nozzle means for jettingcompressed cooling air externally against said envelope intermediatesaid electrodes, said means being arranged to distribute this airsubstantially symmetrically lengthwise of the envelope with respect toits mid-length and in a constricted air stream width, transversely ofthe envelope, substantially less than the envelope width presented tothe impinging air, whereby envelope temperature and devitrification aresubstantially reduced While maintenance of discharge-constrictinginternal pressure is allowed.

NEWELL 'I'. GORDON. WILLIS R. WHITNEY.

